Telecommunications systems, cable television systems and data communication networks use optical networks to rapidly convey large amounts of information between remote points. In an optical network, information is conveyed in the form of optical signals through optical fibers. Optical fibers comprise thin strands of glass capable of communicating the signals over long distances with very low loss. Optical networks often employ wavelength division multiplexing (WDM) or dense wavelength division multiplexing (DWDM) to increase transmission capacity. In WDM and DWDM networks, a number of optical channels are carried in each fiber at disparate wavelengths, thereby increasing network capacity.
An optical signal comprised of disparate wavelengths experiences optical dispersion, a sometimes undesirable phenomenon that causes the separation of an optical wave into spectral components with different frequencies. Optical dispersion occurs because the differing wavelengths propagate at differing speeds. The separation of an optical wave into its respective channels due to optical dispersion requires optical dispersion compensation for the particular optical signal.
Due to the ever-increasing volume and bit rate of data traffic, future transmission equipment will need to be capable of efficiently accommodating high-speed traffic, such as hundred-gigabit-per-second (100 Gb/s) traffic, and also will need to accommodate slower traffic on the same fiber such as 10 Gb/s signals. To receive high-speed signals (which may also include 40 Gb/s signals), a digital coherent receivers having digital signal processors are used. In 10 Gb/s and 40 Gb/s WDM transmission systems using conventional direct receivers (as opposed to coherent receivers), various optical dispersion compensation technologies are used to manage different types of waveform distortion generated in the optical signal. However, the amount and accuracy of compensation achievable with such conventional optical dispersion compensators is inadequate for 100 Gb/s signals. For such signals, a digital coherent receiver provides compensation of waveform distortion beyond the limits of optical dispersion compensation. However, issues still exists with the compensation of signals in such high-speed networks.